diff --git a/dyndnsd.gemspec b/dyndnsd.gemspec
index 791869b..099a68a 100644
--- a/dyndnsd.gemspec
+++ b/dyndnsd.gemspec
@@ -27,7 +27,7 @@ Gem::Specification.new do |s|
 
   s.required_ruby_version = '>= 3.0'
 
-  s.add_dependency 'async', '~> 1.31.0'
+  s.add_dependency 'async', '>= 1.31', '< 2.24'
   s.add_dependency 'async-dns', '~> 1.3.0'
   s.add_dependency 'base64', '~> 0.2.0' # needed for async
   s.add_dependency 'logger', '~> 1.6.0'